Lead poisoning in wild birds from southern Spain: A comparative study of wetland areas and species affected, and trends over time

Abstract

We studied lead (Pb) shot contamination in sediments from the Guadalquivir marshes and six other closed-basin lagoons in Southern Spain that are of major importance for threatened species of waterbirds. Shot densities were relatively low in Doñana, ranging from 0 to 25 shot/m 2 in the top 10 cm of sediments. The density at Medina lagoon (Ramsar site) was 148 shot/m 2, making it the most contaminated wetland known in Europe. Densities in the other five lagoons ranged from 9 to 59 shot/m 2. We studied the prevalence of ingested Pb shot in waterbirds from Doñana and found a lower prevalence in ducks than previously recorded in other Spanish wetlands. Lead shot were also found embedded in tissues of some waterbirds, proving that protected species such as the greater flamingo ( Phoenicopterus ruber) and the glossy ibis ( Plegadis falcinellus) are subjected to illegal hunting. The prevalence of embedded shot for geese was especially high (44% for trapped birds). Lead shot were detected in 2.8% of the pellets of the Spanish imperial eagle ( Aquila adalberti) which usually preys on geese. We found that the prevalence of ingested Pb shot in geese and in Spanish imperial eagles has significantly decreased in recent years, possibly due to restrictions on hunting activity, efforts to remove shot from a sand dune used by geese to obtain grit, and to the high rainfall in Doñana during the last years that permitted waterfowl to stay more within the protected areas.